Photographic silver halide emulsions stabilized with 2-imino-thiazolones



United States Patent Oflice 3,434,842 Patented Mar. 25, 1969 3,434,842 PHOTOGRAIHIC SILVER HALIDE EMULSIONS STABILIZED WITH Z-IMINO-THIAZOLONES Harald Hiickstiidt, Cologne-Stammheim, Wilhelm Saleck, Schildgen, Bergstrasse, Gladbach, Hans Ulrich and August Randolph, Leverkusen, and Herbert Grabhiifer,

Cologne-Flittard, Germany, assignors to Agfa Gevaert J Aktiengesellschaft, Leverkuseu, Germany, a corporation of Germany No Drawing. Filed July 19, 1965, Ser. No. 473,216

Claims priority, application Germany, Aug. 8, 1964, A 46,797 Int. Cl. G03c N34 US. Cl. 96-109 5 Claims ABSTRACT OF THE DISCLOSURE It is generally known that the sensitivity of photographic silver halide emulsions can be increased by adding suitable chemical compounds. Compounds of this type, referred to as chemical sensitizers, include, inter alia, polyalkylene oxides, in particular polyethylene oxides and their derivatives. The addition of such compounds increases the sensitivity and the contrast (gamma) of the silver halide emulsions.

Unfortunately, the use of polyalkylene oxides has the disadvantage that the fog level of the emulsions to which they are added is undesirably increased, with the result that sometimes they cannot be used.

As is generally known, fogging may be counteracted by adding so-called stabilizers or antifogging agents to the emulsions. Several compounds have already been used as staibilizers or antifogging agents, but unfortunately most of them have the disadvantage that they reduce the sensitivity and/or the contrast of the emulsion. Examples of such stabilizers include organic mercury compounds, heterocyclic mercapto compounds and azaindenes.

It has now been found that photographic silver halide emulsions which are chemically sensitized with polyalkylene oxides or their derivatives, may be stabilized against harmful fogging without impairing the original sensitivity or the gamma, by adding to the emulsions compounds of the general formula in which R or R represent hydrogen, alkyl preferably lower alkyl with up to 5 carbon atoms such as methyl or ethyl, aryl preferably phenyl, aralkyl such as benzyl or phenylethyl, or alkenyl, or R and R together can form an ethylene group that completes an imidazoline ring; R represents hydrogen, carboxyl, carbonylamide in which case the amide group may be substituted in particular with short-chain alkyl radicals with up to 5 carbon atoms, esterified carboxyl in particular with aliphatic alcohols containing up to 18 carbon atoms, preferably with those containing up to 5 carbon atoms, or with cycloaliphatic alcohols such as cyclohexanol; n is 0 or 1 and X represents any acid anion, preferably a halogen ion.

Of the compounds corresponding to the above general formula, those in which at least one of the substituents R, R or R is different from hydrogen, are preferred for the purposes of this invention. This applies in particular as regards the substituents R and R Where R represents hydrogen, the stabilizersaccording to the invention may be tautomers according to the following equation:

The following compounds have proved to be particularly suitable:

H CH2 HO O C .HOl

S NH

H CH

H50200CT .H Oll .HCI

(III) VII H on2 lLHgsCmOO C S NH VIII

D D D \V, W D X 1 H 1 v X X X X X m m H H H H m m m H H r B r H H H l O G w H HF m 4 I m 0 c F N H OHM m w 2 H l l 2 O 0 0 1 ols I 0' I It 2 N 2 N a "N H H V H OIS OIS OIS 2 4 7 M 5 m H m H m H 4 \1 1 m o 1 3 m H m U. 1C1 O H mm a o c m H H N H w w a u H N F o H N NH O H s IN H\ I T H a c H H s vfl c N m V N H o H H 0 VA 5 O w VHNIO N O. o H H H s H N w m m. a. m w H H (XXVII) D H V X m m C 2 /H C N 0 5 D V m m m 0 C K Y 2 N H S (XVII) (XXIX) (XVIII) (XXX) (XIX) 7O (XXXI) The preparation of the Compounds I to X is described in Zeitschrift fiir Angewandte Chemie, 74, page 906 (1962). The substances XIII and XIV are obtained by reacting the respective carboxylic acids with ethylamine. (XX) 75 The Compound XV is prepared in accordance with the prescription in the aforementioned paper while replacing hydrogen chloride by hydrogen bromide. Compounds of the type represented by the Formulae XI, XII, XVI to XXXI are obtained by reacting thiourea derivatives with chloroacetic acid or bromoacetic acid. This method is explained with reference to the following, specific example for Compound XII. This method is described in broad terms in the article by Lieberman and Lange in Liebigs Ann. 207, 128 (1881). As indicated by the above specific examples such compounds of the general formula in which n corresponds to 0 are prepared in which R stands for hydrogen.

Preparation of Compound XII 10.4 g. of N,N'-dimethylthiourea (0.1 mol) and 9.45 g. of chloroacetic acid (0.1 mol) are separately dissolved in methanol. The solutions are combined and refluxed for two hours. The methanol is then distilled off, leaving behind a yellowish crystalline mass from which pale yellowish crystals decomposing above 210 C. are obtained after recrystallization from methanol/ ether.

In the case of silver halide emulsions mixed with polyalkylene oxides, the compounds of the present invention produce a marked reduction in fogging both when the emulsions are fresh and after they have been stored in a heating chamber.

The compounds of the present invention also have the effect of reducing fogging in cases where developing is carried out over a prolonged period.

The emulsions used are chemically sensitized with chemical sensitizers containing a polyalkylene oxide group, preferably a polyethylene oxide group, such as polyalkylene oxides or with polyalkylene oxide derivatives, particularly with polyethylene oxides or their derivatives. Examples of such polyethylene oxides are given in -U.S. Patents Nos. 2,423,549 and 2,441,389.

Polyethylene oxide derivatives are obtained by condensing a polyethylene oxide with compounds containing an active hydrogen atom. Suitable organic compounds with active hydrogen atoms are for instance alcohols, primary or secondary amines, acids, amides and phenols, such as monohydric saturated or unsaturated alcohols having 1 to 20 carbon atoms, e.g., ethanol, dodecanol, stearyl alcohol and oleyl alcohol, polyhydric alcohols, e.g., glycols, glycerol, pentaerythritol, trimethylol propane, aliphatic primary or secondary amines, e.g., N- rnethyl-N-dodecylamine, aliphatic carboxylic acids, e.g., lauric acid, stearic acid, oleic acid or the amides of these acids, and phenol and alkyl phenols, e.g., p-dodecyl phenol. Preferred derivatives of polyalkylene oxides are reaction products of alkylene oxide or of their polymers with compounds containing hydrocarbon radicals with to 10 carbon atoms. The quantity used will depend upon the silver halide content of the emulsion to which the compounds are added. It can vary from 0.01 g. to 1 g. per 1 kg. of silver halide emulsion. The preferred quantity being 0.05 to 2 g. per 1 mol of silver halide. The optimum quantity can easily be established empirically for each emulsion.

Suitable chemical sensitizers of the above type may be illustrated by the following formula:

R OtCH -CH O-l H wherein R stands for hydrogen, an aliphatic hydrocarbon radical (e.g., ethyl, dodecyl, oleyl), an acyl radical of an organic carboxylic acid (e.g., lauric acid, oleic acid), a phenyl radical (e.g., phenyl, p-dodecylphenyl) and n=an integer greater than about 30.

Examples of such polyalkylene oxides can be found in US. Patents Nos. 2,240,472 and 2,400,532. The preferred chemical sensitizers to be used according tothe present invention are phosphorus-containing derivatives of polyalkylene oxides especially those disclosed in US. patent application Ser. No. 368,714, filed May 19, 1964, now US. Patent 3,385,708, granted May 28,1968 and No. 379,738,

6 filed July 1,1964, now US. Patent 3,385,704, granted May 28, 1968.

These compounds are either the condensation products of 1 mol of a spirocyclic pentaerythritol-di-(phosphoric acid monohalide) and 1 to 2 mols. of a polyethylene glycol having between 3 and ethylene oxide units, or the condensation products of 1 mol of a monoamido phosphoric aci dderivative and 1 to 2 mols of a polyethylene glycol having 3 to 100 ethylene oxide units. These compounds may be represented by the following formulae:

wherein n stands for 3 to 100, x stands for l to 10 and R stands for hydrogen or for the group HtO-CHyCHfi wherein n has the same meaning as above, and

Al 1LT AJ Rl Rz X wherein In Belgian patent specification No. 621,607 similar stabilizing additives are used .for the quick processing of silver halide emulsions. t

In that case, the meaning of the term stabilizing differs from its significance in the context of the present invention. According to the Belgian patent specification, such compounds are used to convert the photosensitive sliver halide into a nonphotosensitive complex form. For this purpose, the compounds in question are used in much large quantities than in the present invention, i.e.., not less than 1 mole per mol of silver halide. As far as the present invention is concerned, these compounds cannot be used in such large quantities because they would produce an excessive loss of sensitivity and, at the same time, an increase in fogging.

In German patent specification No. 1,150,277 heterocyclic compounds of the type used according to the present invention are used in combination with elementary sulphur or compounds yielding sulphur, as chemical sensitizers. There is no reference in that patentspecification to the eifect of these compounds as stabilizers in emulsions containing as a chemical sensitizer a polyethylene oxide.

The combination of compounds according to the present invention is effective when used with all types of silver halide emulsions such as silver chloride emulsions, silver chlorobromide emulsions and silver iodochlorobromide emulsions, but preferablywith silver halide emulsions the silver halide of which comprises silver bromide and up to 10 mol percent of silver iodide. The compounds may be added to the emulsion at any stage during its preparation, but preferably after it has been chemically ripened. They are used in quantities of 0.1 to 15 g., preferably 0.5 to 5 g. per mol of silver halide. The emulsions may be optically sensitized or nonsensitized and may contain color couplers. They may also be sensitized with noble metals such 1 as gold salts. In addition to the additives according to the invention, the emulsions may contain other conventional additives such as antifogging agents, wetting agents, gelatin plasticizers or gelatin hardeners.

EXAMPLE 1 A panchromatically sensitized highly sensitive silver iodobromide emulsion (6 mol percent of silver iodide) 8 EXAMPLE 2 A highly sensitive silver iodobromide emulsion similar to that described in Example 1 except that, in place of the polyalkylene oxide used in that example, it contains 0.16 g. per liter of a chemical sensitizer corresponding to the following formula:

0 1 Ff H H- OCHzGHz -0P P-OH OCH2CH2/O1| on L\ A l| IU 1a N CH3 1.4

l is tested as described in Example 1. The results of the tests are given in the following Table II.

The preparation of the polyalkylene oxide corresponding to the above formula is described in US. Patent No. 3,169,863 under its Compound V.

TABLE II Amount 3 days storage in heating Stabilizer added pier Fresh emulsion chamber at 60 C.

1 re 0 emulsion, g. Sensitivity, Gamma Fog level Sensitivity, Gamma Fog level Sample:

A1 Standard 0.80 0.15 0.80 0. 23

B I.-. 0.48 d 0.75 0.15 0.75 0.16

D... IX 0. 48 0. 75 0.13 0.75 0.17

Standard.

and is divided into three parts. Each part is then mixed EXAMPLE 3 with the quantities indicated in the following table of one of the stabilizers according to the present invention, and is then cast in the usual way onto a transparent substratum consisting of, for example, cellulose acetate, and dried. The polyalkylene oxide corresponding to the above formula is prepared according to the prescription given in German patent specification No. 1,182,523.

TABLE III Amount 3 days storage in heating Stabilizer addted pfer Fresh emulsion chamber at 60 C.

1 re 0 emulsion, g. Sensitivity, Gamma Fog level Sensitivity, Gamma Fog level Sample A 0- 55 0. 22 l. 5 0. 55 0.33 B.-. XII 0. 48 +1. 0 0. 65 0. 15 0. 65 0. 18 C.-. VI 0 48 0. 55 0.17 0.50 0. 20

1 Standard.

Each sample is exposed behind a step wedge and then EXAMPLE 4 developed for about 8 to 10 minutes at 20 C. to approximately the same gamma value in the following developer mixture:

Grams p-Methylaminophenol sulfate 3 Sodium sulfite (anhydrous) 8O Borax 10 Potassium bromide 0.5 Made up with water to 1 liter.

The relative sensitivity, gamma values and the fog level are determined by the usual methods. The results are given Portions of a silver iodobromide emulsion of the type described in Example 1 are mixed with diflferent chemical sensitizers and additives according to the present invention, as shown in the following Table IV, and are cast onto a transparent substrate, each forming a layer of equal thickness thereon, and then dried. They are developed in a hard-type developer for 10 minutes at 20 C., until the gamma value is 2 to 3.

The developer has the following composition:

Grams p-Methylaminophenol sulfate 5 Sodium sulfite (anhydrous) 40 Hydroquinone 6 Potassium carbonate 40 Potassium bromide 3 in the following Table I. Water to make up to 1,000 mi.

TABLE I Amount 3 da s st i h ti Stabilizer added per Fresh emulsion (518111831 53 1; iii) ii. mg

emulsion, g. Sensitivity, Gamma Fog level Sensitivity, Gamma Fog level 1. 5 O. 05 0. 19 l. 0 0. 65 0. 13 1. 0 0. 65 0. l3

1 Standard.

The results of the tests are given in the following Table IV:

3. A photosensitive material as claimed in claim 2, wherein R represents alkyl.

TABLE IV Stabilizer Sensitizer (0.16 Fog level Fog level (0.48 g./ g./litre of emulsion) after 5 minutes after litre of development minutes emulsion) development;

Sample:

A As in Example 1.-- 0. 17 0. 19 B XII do 0.11 0.14 c v1 do 0.11 0.15 A As in Example 2.-- 0.22 0.30 B 1 (in 0.18 0.21 0. II --d0 0. 23 0.26 D- IX- do 0.16 0. A1- As in Example 3..- 0.31 0.34 B XII do 0418 0.26 0 VI do 0.20 0.26

Standard.

We claim: 20 4. A photosensitive material as claimed in claim 3, 1. In a photosensitive photographic material which comwherein the stabilizer corresponds to the formula prises at least one silver halide emulsion layer containing a chemical sensitizer having a polyalkylene oxide group, 1 H01 the improvement according to which said emulsion layer s N--CH3 has added thereto in stabilizing quantities a stabilizer of 25 the general formula 1;

H\ )GEM 5. A photosensitive material as claimed in claim 1 (3 0:0 wherein R and R represent hydrogen, alkyl having up l to 5 carbon atoms, phenyl, benzyl or phenylethyl, R 1 represents hydrogen, carboxyl, carbon amide, alkyl subfi stltuted carbon amide having up to 5 carbon atoms in N each alkyl group, esterified carboxyl having up to 18 car- I bon atoms or cycloalkyl. R

References Cited wherein UNITED STATES PATENTS R and R represent hydrogen, alkyl, aryl, aralkyl or 2,131,033 9/ 1938 o er e a1 96-109 lk l, 3,189,453 6/1965 Herz et al 96-61 R represents hydrogen, carboxyl, earbonylamide or es- 3,321,312 5/1967 a dorfi et a1. 96-109 terified carboxyl, n is 0 or 1, and X represents any acid anion. 2. A photosensitive material as claimed in claim 1, wherein at least one of the snbstituents R, R or R is different from hydrogen.

NORMAN G. TORCHIN, Primary Examiner.

J. -R. EVERETT, Assistant Examiner.

US. Cl. X.R. 96--66.5 

